1. Field of the Invention
The present invention relates to a high voltage generating circuit for generating high voltage, an ion generating device having the high voltage generating circuit for emitting ions into a space so that a room environment can be improved, and an electrical apparatus equipped with the ion generating device. Note that the above-mentioned electrical apparatus may include an air conditioner, a dehumidifier, a humidifier, an air cleaner, a refrigerator, a fan heater, a microwave oven, a washing machine with a dryer, a cleaner, a pasteurizer and the like, for example, used mainly in a closed space (indoor, a room in a building, a sickroom or an operating room in a hospital, a car interior, a cabin of a plane or a ship, a warehouse, a chamber of a refrigerator and the like).
2. Description of Related Art
Generally speaking, if a large number of people are in a closed room such as an office or a meeting room with little ventilation, air pollutant including carbon dioxide exhausted by breathing, tobacco smoke, dust and the like increases so that minus ions having an effect of relaxing people may decrease in the air. In particular, existence of tobacco smoke may decrease the minus ions to approximately ½ to ⅕ of a normal state. Therefore, various types of ion generating devices are on the market conventionally in order to supply minus ions in the air.
However, all the conventional ion generating devices are the DC high voltage type that generates only minus ions by a DC voltage. Therefore, such the ion generating devices cannot actively remove floating germs or the like in the air though they can supply minus ions in the air.
In view of the above-mentioned problem, the applicant has invented the ion generating device that generates H+(H2O)m as plus ions and O2−(H2O)n as minus ions (m and n are natural numbers) in the air in substantially the same quantity, which are adhered to the floating germs or the like in the air so that the floating germ can be removed by decomposing action of active hydrogen peroxide (H2O2) and/or hydroxyl radical (•OH) generated on the occasion (see JP-A-2003-47651, for example).
Note that the above-mentioned invention is already brought into a practical use by the applicant. There are practical apparatuses including the ion generating device having a structure in which a discharging electrode is disposed outside a ceramic dielectric while an induction electrode is disposed inside the same, and the air cleaner, the air conditioner or the like equipped with the ion generating device.
FIG. 15 is a circuit diagram showing a conventional example of the ion generating device that can generate H+(H2O)m as plus ions and O2−(H2O)n as minus ions (m and n are natural numbers) in substantially the same quantity. The conventional ion generating device shown in FIG. 15 has a high voltage generating circuit for generating AC impulse high voltage and a discharging portion X1 for generating ions by discharging the high voltage applied from the high voltage generating circuit. Furthermore, the above-mentioned high voltage generating circuit includes a resistor R1, a diode D1, a capacitor C1, a transformer T1 and a semiconductor switching element S1.
In the conventional ion generating device shown in FIG. 15, the output voltage of the commercial AC power source E1 is dropped by the resistor R1 and is rectified by the diode D1 as half-wave rectification, which is applied to the capacitor C1. When the capacitor C1 is charged until the terminal voltage E2 of the capacitor C1 shown in FIG. 16A increases to a predetermined threshold value VTH shown in FIG. 16A, the semiconductor switching element S1 is turned on so that the charged voltage of the capacitor C1 is discharged. This discharge causes current flowing in the primary winding L1 of the transformer T1 so that energy is transmitted to the secondary winding L2. As a result, the AC impulse high voltage E3 shown in FIG. 16B is applied to the discharging portion X1. Just after that, the semiconductor switching element S1 is turned off, so that charging of the capacitor C1 is restarted.
The changing and the discharging described above are repeated, and thus the AC impulse high voltage shown in FIG. 16B is applied to the discharging portion X1 repeatedly. On this occasion, corona discharge is generated in the vicinity of the discharging portion X1 so that the ambient air is ionized. As a result, plus ions of H+(H2O)m are generated when the positive voltage is applied while minus ions of O2−(H2O)n are generated when the negative voltage is applied (m and n are natural numbers). Therefore, it is possible to make both ions be adhered to the floating germs or the like in the air so that the floating germ can be removed by decomposing action of active hydrogen peroxide (H2O2) or hydroxyl radical (•OH) composing action generated on the occasion.
It is sure that the conventional ion generating device shown in FIG. 15 can actively remove floating germs or the like in the air, so the room environment can be improved to be more comfortable.
However, the above-mentioned conventional ion generating device shown in FIG. 15 has a problem as follows. Since it uses the commercial AC power source E1 as an input power source, it needs the capacitor C11 with high withstand voltage and large capacitance and the semiconductor switching element S1 with high withstand voltage discharge for storing energy in the capacitor C1 temporarily and switching between charge and discharge of the capacitor C1 by the semiconductor switching element S1, which causes increase in the size.
In addition, the above-mentioned conventional ion generating device shown in FIG. 15 cannot adjust the voltage to be applied to the discharging portion X1 since the predetermined threshold value VTH of the semiconductor switching element S1 and a voltage transforming ratio of the transformer T1 determine the voltage to be applied to the discharging portion X1. Therefore, it has a problem that the discharging portion X1 may be broken down when voltage exceeding the withstand voltage of the discharging portion X1 is applied to the discharging portion X1.
In addition, the above-mentioned conventional ion generating device shown in FIG. 15 cannot adjust the voltage to be applied to the discharging portion X1, which is determined by the predetermined threshold value VTH of the semiconductor switching element S1 and the voltage transforming ratio of the transformer T1. Therefore, the same high voltage generating circuit thereof cannot support the case where the discharging portion X1 has a different material or shape so that the discharge start voltage of the discharging portion X1 is different.
In addition, the above-mentioned conventional ion generating device shown in FIG. 15 has the problem that the number of discharge times of the capacitor C1 per unit time, i.e., generating quantity of ions cannot be adjusted arbitrarily because the discharge energy is stored in the capacitor C1 temporarily.
In addition, the above-mentioned conventional ion generating device shown in FIG. 15 has a following problem. If the capacitance of the discharging portion X1 increases due to deterioration of the discharging portion X1 or adherence of foreign substances or the like, the output voltage from the high voltage generating circuit will be dropped (see FIG. 17). When the output voltage becomes below the discharge start voltage of the discharging portion X1, the discharge may stop, i.e., generation of ions may stop.